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Prevention of Overfishing of Coral Reefs Reduces Occurrence of Coral Diseases

Beautiful coral formations in Key Largo, Florida.

Beautiful coral formations in Key Largo, Florida. Photo courtesy of Stig Nygaard via Flickr (attribution link below).

In 1975 I saw my first coral reef (John Pennekamp Coral Reef State Park), and in May 2009 I had a chance to do a little snorkeling in the Dry Tortugas.  I’m looking forward to going back soon to snorkel more reefs in the Florida Keys.

Anyone who has ever seen a coral reef can tell you that it is one of the most beautiful things you can see under the water. A scientist will tell you that a coral reef is the most diverse of all marine ecosystems. That means a coral reef supports a greater number of unrelated animal and plant species than does any other marine environment. Florida is unique in that it has the only living coral reefs in the continental United States. Protecting those reefs from damage and disease for future generations is essential.

My long-time friend Dr. Alexander Kerr, of the University of Guam’s marine lab, recently sent me a copy of a study he co-authored titled “Functionally diverse reef-fish communities ameliorate coral disease.” I thought I’d summarize their findings here because even though the underwater study was conducted in the Phillipines, the findings are noteworthy to anyone concerned with coral reefs.

The study “tested the hypothesis that reefs with more intact fish communities had significantly lower levels of coral disease.”

The researchers compared coral reefs in Marine Protected Areas  where fishing is banned with nearby reefs where fishing is allowed. What they found is that reefs that were protected from over-fishing had more diverse fish populations and less damage from coral diseases.

When fishing removes food-fish like grouper from the reef, it provides an opportunity for non-food fish, like the Butterfly fish (Chaetodontids), to thrive.  Butterfly fish feed directly on the coral and are believed to carry and spread coral diseases.

A colorful Butterfly fish swims above a coral reef. Photo courtesy of Roger Braunstein.

A colorful Butterfly fish swims above a coral reef. Photo courtesy of Roger Braunstein via Flickr (attribution link below).

What the study reveals is that Butterfly fish are more abundant on over-fished reefs and that higher populations of Butterfly fish are associated with higher levels of coral diseases affecting the reef.

The study suggests that by regulating (not banning)  fishing, diversity can be maintained in fish communities. Keeping fish species diversity intact on a reef may reduce the incidence of coral diseases and result in healthier coral reefs.

Resources related to this post:

BBC article about the study.

Abstract of the  study at Proceedings of the National Academy of Sciences.

Study authors: Laurie J. Raymundo, Andrew R. Halford, Aileen P. Maypa, and Alexander M. Kerr.

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